The present invention relates generally to the field of fluid flow rate control mechanisms, and, more specifically, to an assembly or system of interconnected, interfacing valves for provision of fluid in either a constant or pulsed flow mode, and at multiple selectable rates with precise regulation thereof in either mode.
The new fluid valve assembly or system includes valve means developed especially for metering the flow of oxygen to a patient. However, the new assembly can also be used to meter fluids other than gaseous oxygen to a patient or some known device. For medical purposes, it is necessary to provide patient gases at very precise levels in a controlled manner, and ideally by means which are easily portable.
The new system is ordinarily used in conjunction with a pressurized source of liquid oxygen which is usually provided at either 20 psig or 50 psig. As the pressurized liquid oxygen comes out of an insulated bottle or other container it evaporates into a gas. The fluid flow rate control valve of the new system accepts the gaseous oxygen phase from either of the standard 20 psig or 50 psig sources, as may be convenient for the particular user, after passage of the fluid through a heat exchanger in the usual manner. The system may also be used with fluid sources having pressures other than those specified above as standard. For example, even pressures as low as 5 psig or as high as 100 psig could be used with the new assembly.
The pressurized gas (in this example, oxygen) goes through an orifice, a very small, finely calibrated hole, which meters out distinct fluid flow rates to the patient. The new valve has two distinct sets of such holes, one for supplying oxygen to a patient on a continuous basis and one for providing relatively larger volumes of oxygen in a short time span, so as to be "pulsed". Ordinarily doctors prescribe oxygen to patients at a constant rate of so many liters per minute, for example, anywhere in the range of from about 0.25 to about 15 liters per minute to a patient. As the doctor prescribes a certain dosage of oxygen to a patient, the flow control valve of the new system allows the patient to select the prescribed flow mode of oxygen delivery.
There is also another means of administering oxygen other than a standard constant flow. The alternate mode is to "pulse" out a dose of oxygen, the same volume the patient would normally breath in over the space of an entire inhalation, except that it is suddenly dosed out in one large volume on the initiation of inhalation by the patient, because the patient only receives oxygen during active inhalation. When the patient exhales and the oxygen administration system is in a continuous flow mode, oxygen is wasted. Thus, the intent is to deliver oxygen to a patient only upon inhalation demand as indicated by an electronically sensed pressure drop. Thus, by pulse delivering intermittent large volumes, approximately one third less than the normal amount of oxygen is used, the net result being an oxygen system weight reduction, a cost reduction (less total oxygen used), and a gain in patient mobility by provision of the patient with a smaller package.
In the pulsing mode it is often desired to administer in a shorter time span an amount of oxygen which is the equivalent of approximately 16 cc of oxygen per one liter of total fluid per minute of fluid flow. The rate control valve of the new valve assembly provides at least two groups of graduated orifices to permit oxygen dose metering. The holes in the second group of orifices in the flow control valve are designed to meter out a uniform volume of oxygen over a short time span, i.e., to "pulse" out the flow intermittently upon demand which is signalled by a pressure drop caused by inhalation. This time period is normally about 0.4 of a second, so that when the patient inhales, immediately, within approximately the first 0.4 seconds of the inhalation, a volume of oxygen that is equivalent to 16 cc of oxygen per liter of fluid, as normally prescribed, is pulsed out through the system. Thus the new rate control valve permits the assembly to deliver patient oxygen much more efficiently than was previously known.
The flow rate control valve of the new valve assembly has two at least two different sets of orifices. One is for continuous flow to the patient and the other for pulsing flow, as mentioned. The pulsing flow necessarily has a larger range of hole sizes because a larger volume must be provided in one dose.
In order for the patient or doctor to choose between the pulsing mode and the continuous flow it is also necessary to have a valve that toggles or otherwise is switchable between either one or the other of the two flow modes. Thus, the new fluid valving assembly also includes a mode selector valve allows us to choose which flow type the patient will receive. If the patient is on continuous flow, the administrator just opens up the holes and allows flow going directly to the patient. If, however, the patient is to receive oxygen in the pulsed mode, fluid outlet and inlet ports that admit larger volumes and meter out the pulsed flow to the patient are selected.
The new fluid flow mode control valve permits a choice between either the smaller or larger port and has incorporated an electrical switch that sends a signal to a circuit board to indicate that the valve is in the pulse mode, and thereby directs a solenoid valve to open up and pulse out the metered flow of oxygen. The circuit board and the solenoid valve are provided from and function according to commonly available technology. The new valve system provides a means of delivering oxygen in either fixed (continuous) flow or pulsing flow and a means of turning on and off the electronic signalling device as will be clear from the following description.
One major purpose of the new system is to provide an improved apparatus for supplying prescribed oxygen to a patient, as discussed. However, the new fluid flow control valve assembly provides such a wide range of controlled fluid transfer options that it can also be well utilized in many other areas, for example,laboratory research, and industrial research and applications, such as the automotive industry. Furthermore, particular fluids which are foreseen to be used in the new system include nitrogen, helium, argon, etc.
The new valve system can also conceivably be used in a reverse flow mode to mix different fluids, such as oxygen and acetylene, in very precise proportions to achieve a fluid mixture of exactly controlled content, for a similarly wide variety of possible uses.
Previously, fluid control valves have been known for many uses. However, for a variety of reasons these known valves have been unsuitable for provision of medical grade oxygen to a patient. Some valves are intended only for uses requiring very high volumes, and thus cannot be miniaturized so as to be easily portable, especially when combined with other necessary equipment. Those and other known valves are not capable of fine calibration for the precise amount of fluid to be delivered, nor can the mode of delivery (constant or pulsed) be selectively altered as required for a particular application.
Also, many other known valves do not include fail-safe features which ensure that the fluid flow through the valve or valve assembly will always be available, regardless of mode switch position. Of course, in the case of a patient requiring supplemental oxygen it can be critical to the patient's life that the oxygen supply never be eliminated. It is also necessary that patient oxygen be precisely controlled in order to neither "starve" or "burn" the patient.
The known valve art does not suggest a patient oxygen system including a valve with multiple fluid flow rates and alternate flow modes, nor a fluid control valve configuration where the rate control valve body is provided with multiple outlet orifices which are integrated with multiple valve flow rate settings. Also, no system is known in which the same valve assembly design can be used selectively for either multiple flow modes or a single flow mode, the rate control valve configuration predetermining which track of apertures in a flow control plate is used.
This is particularly the case when considered with the feature of the flow control plate being a wafer-thin metal (eg. stainless steel) plate formed with circular tracks of tiny apertures of graduated size to control the flow rate, in such manner as to provide extremely high accuracy of the type required for oxygen administration ranging from pediatric levels up through emergency volumes. Further detailed discussion of such flow plates may be found in U.S. Pat. Nos. 4,572,477 and 4,643,215, which are incorporated herein by reference. In the flow rate control valve of the new assembly multiple sets or tracks of apertures or through-holes are provided so that it would be possible to have even three different flow rate levels, such as pediatric (lowest volume per unit time), normal (middle volume per unit time), and emergency (highest volume per unit time).
Thus, the new system can provide different flow control modes to permit calibrated oxygen flow either continuously, or as a pulsed oxygen supply system in which flow is provided on a pressure-demand basis by pressure-drop sensing by a control unit. Dual outlets, one for low volume constant-flow and the other for a pulsed flow at a rate which is variably from about two to about six times higher volume, based upon pressure-demand.
The multiple flow rate valve of the new system provides accurately calibrated flow regardless of whether there is system transition from one flow mode to the other, as in a portable oxygen system wherein a solenoid valve controls demand flow, but structure exists for switching to constant-volume flow if desired or necessary, such as in the event of a power failure, during which the automatic pressure sensor would not function (unless battery supplemented).
The known art also does not include patient oxygen or other fluid supply systems which feature a spool-valve design which is fail-safe in that fluid will continue to be supplied regardless of the switch position. The new valve spool design allows for both a low volume flow and a higher volume flow without flow-blocking elements or other compromises of patient safety. Moreover, the extremely compact design of the new flow mode selector valve incorporates a microswitch which is directly connected to the body of the unit for constant automatic electrical sensing of the flow mode position of the valve and reporting to a flow mode and pressure-sensing control circuit.
The flow mode valve portion of the new assembly is designed to provide for selectively toggled switching between constant flow mode and pressure demand flow mode control of gases in a pulsed oxygen supply system wherein oxygen is supplied on a pressure-demand basis by pressure drop sensing in the control unit. This switchable valve is formed with a spool-like shaft and includes a fluid outlet port which is positioned relative to sealing O-rings and is dimensioned relative to the O-ring longitudinal extent such that it will never be blocked, regardless of whether the valve shaft upon which the O-rings are mounted is toggled to one flow control position or the other, or even inadvertently somewhere intermediate (e.g. because toggling was incomplete). In this manner the unit is fail-safe, in that fluid will continue to be supplied no matter which switch position it is in, and the spool shaft design allows for both a low volume flow and a higher volume flow without flow-blocking elements.
Accordingly, it is among the several objects of the invention to provide an assembly of valves for provision of fluids in a manner in which the flow rate is highly controlled and amenable to precise calibration at both relatively high and low rates of flow, as well as being capable of use in either a continuous or pulsed flow manner. It is desired that the new system be especially suitable for use in supplying oxygen to patients, which may be children as well as adults, and in emergency situations as well as for long-term care.
It is further among the objects of the invention, having the features mentioned, to provide a fail-safe feature to ensure that regardless of the position of the mode control valve switch, fluid can always be passed through the "three-way" mode control valve and also that such valve be miniaturized for convenience of use and that it be provided with an electric switch for automatic sensing of the valve setting, whether for pulsed or continuous flow.
It is also among the several objects of the invention to provide an assembly having the features enumerated in which the various valving features can be provided either by a plurality of independent valves which are indirectly interconnected, or alternatively, by such valves in a combined construction, so directly connected that they essentially form a single unit which performs combined valving functions.
It is still further among the several objects of the invention that the new valve assembly or system provide metered delivery of fluid therethrough in an economical, fluid-conserving manner, so as to prevent inadvertent exhaustion of fluid supplies, and that the valve system components be suitable for manufacture from a variety of materials so as to amenable to various use requirements and economic and manufacturing constraints.
Thus, in furtherance of the above objects, the invention is, briefly, a multiple flow rate fluid control valve assembly in which the mode of fluid flow is interfaced with the rate of fluid flow. The assembly includes a first valve having a switch for selectively setting the valve to one of a plurality of selectable fluid flow modes. A second valve is connected to the first valve for selectively controlling the rate of fluid flow from a source of fluid through the second valve to the first valve, to thereby provide fluid from the source of fluid to the first valve at a rate which is appropriate for the mode of fluid delivery and the particular fluid use.
Also with regard to the new assembly, briefly, the shaft has a depression formed therein, and the first valve further includes a sensor for automatically sensing the flow mode in which the first valve is set. The sensor contacts the shaft at a point immediately adjacent the depression when the shaft is in one flow mode position and is removed from contact with the shaft when the first valve is switched to be in the other flow mode position due to longitudinal movement of the shaft within the bore until the depression formed in the shaft comes into alignment with the sensor.
The invention is also, briefly, the assembly just described, wherein the second valve is a flow rate control valve having an upper body portion and a lower body portion connected to the upper body portion. A flow control plate is rotatably mounted between the upper body portion and the lower body portion. The flow control plate has a plurality of tracks of apertures of graduated size for selectively controlling the amount of fluid which can pass therethrough as the fluid is transferred from the second valve to the first valve.
Furthermore, the plurality of tracks of apertures are formed as concentric rings of apertures of graduated size, the apertures of the outermost ring having diameters over a range which is greater than the diameter of any of the apertures in an innermost ring.
The invention is further, briefly, the assembly above, wherein the flow control plate is adapted for selective use of the second valve to provide fluid to the first valve at a predetermined flow rate which can be precisely controlled whether the first valve is in a continuous or a pulsed flow mode.
The invention is also, briefly, a fluid flow mode control valve for use as part of an assembly of valves for provision of fluid in a preselected delivery mode and at a preselected rate. The fluid mode control valve includes a valve body defining at least two inlet openings for receiving fluid from a fluid source at different preselected rates, which rates are preselected depending in part upon the preselected delivery mode, an outlet opening for release of fluid in the preselected delivery mode, and a throughbore in communication with each of the at least two inlet openings and in communication with the outlet opening. A shaft is slidably disposed within the through-bore, and a switch is connected to the shaft for selective moving of the shaft within the through-bore to cause a change in which of the at least two inlet openings is in communication with the outlet opening, to thereby selectively change the mode of fluid delivery through the flow mode control valve.
Other objects will be in part apparent and in part pointed out hereinbelow.